Collect and report kernel warnings.
A flex-based daemon collects kernel warnings by parsing /var/log/messages
as lines are added to it. For every warning the daemon sends a sample
to a sparse UMA histogram using a hash of the warning as the bucket.
Then, if the warning hasn't been seen before, the daemon invokes the
crash collector to upload the warning stack trace.
BUG=chromium:217382
TEST=manually tested (for now), automated test on its way
CQ-DEPEND=Ic8d5773d05d717a275c4a4b5616e0e4c307337b8
CQ-DEPEND=I6a4010acad0ffe20c702bb0fc455e3da7cdf3ac1
Change-Id: I89090e5c2b61ec46b4e740f0895c591728d70e77
Reviewed-on: https://gerrit.chromium.org/gerrit/48277
Commit-Queue: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Tested-by: Luigi Semenzato <semenzato@chromium.org>